General Mechanical

General Mechanical

creep doesn’t converge

    • Oelot

      Hi, I'm trying to study the creep for a tensile specimen, but my solution does not converge.

      I turned on Newton-Raphson residual plots to see what happen ( 

      I have this (the problem is on the surface where the force is applied. )

      I'm thinking about the problems, maybe my Norton's creep parameters are wrong, I calculate them from a curve :

      Norton Law : creep strain rate = A* sigma^n * time^m 

      I deduced the 1st creep parameter is  A, the second is n, and the third is m in the engineering data.
      And the value I found for them are :

      1st = 0,25, 2nd = 20,58 and third = 1, I put these value in the engineering data.( are they realistic ? )

      NB : I did a simple tensile test, by putting a fixed  support in one side, and by applying a force in the other.

      Thanks you

    • peteroznewman

      Here is a relevant post.

      You don't have the equation for Norton correct. See the post I linked to.

      Creep constants depend on the Units you are in.  You need different constants if you are in psi than if you are in Pa or MPa.

      Here is a post about getting creep to converge.

    • gopikrishna

      i need to simulate a round bar for creep in which one end is fixed and other is applied by a tensile load. the problem is my simulation is not converging. i have tried changing substeps, applied fine mesh, rechecked creep constants and units still problem exists. please help me to sort out this problem.

    • peteroznewman

       Okay, I will lock this Discussion and anyone can reply to your discussion linked to above.

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